Comparison of Industrial Quenching Oils

This article is a response to the state of the art in monitoring the cooling capacity of quenching oils in industrial practice. Very often, a hardening shop requires a report with data on the cooling process for a particular quenching oil. However, the interpretation of the data can be rather difficult. The main goal of our work was to compare various criteria used for evaluating quenching oils. Those of which prove essential for operation in tempering plants would then be introduced into practice. Furthermore, the article describes monitoring the changes in the properties of a quenching oil used in a hardening shop, the effects of quenching oil temperature on its cooling capacity and the impact of the water content on certain cooling parameters of selected oils. Cooling curves were measured (including cooling rates and the time to reach relevant temperatures) according to ISO 9950. The hardening power of the oil and the area below the cooling rate curve as a function of temperature (amount of heat removed in the nose region of the Continuous cooling transformation - CCT curve) were calculated. V-values based on the work of Tamura, reflecting the steel type and its CCT curve, were calculated as well. All the data were compared against the hardness and microstructure on a section through a cylinder made of EN C35 steel cooled in the particular oil. Based on the results, criteria are recommended for assessing the suitability of a quenching oil for a specific steel grade and product size. The quenching oils used in the experiment were Houghto Quench C120, Paramo TK 22, Paramo TK 46, CS Noro MO 46 and Durixol W72.

Study on Phase Transformation in Hot Stamping Process of USIBOR® 1500 High-Strength Steel

Based on the Kirkaldy-Venugopalan model, a theoretical model for the phase transformation of USIBOR® 1500 high strength steel was established, and a graph of the phase transformation kinetics of ferrite, pearlite, and bainite were plotted using the software MATLAB. Meanwhile, with the use of the software DYNAFORM, the thermal stamping process of an automobile collision avoidance beam was simulated. The phase transformation law of USIBOR® 1500 high-strength steel during hot stamping was studied through a simulation of the phase transformation during the pressure holding quenching process. In combination with the continuous cooling transformation (CCT) curve, the cooling rate of quenching must be greater than 27 °C/s to ensure maximum martensite content in the final parts, and the final martensite content increases as the initial temperature of the sheet rises.

Test and Research on Controlled Cooling Technology for High Carbon High Silicon Wire Rod of S87B

In this paper, critical temperature of phase transformation and continuous cooling transformation (CCT) curve of S87B were determined by hot uniaxial compression tests. At several of cooling speed, the microstructures were studied. The results indicate that the critical temperature of phase transformation become lower with cooling speed increasing, the min interlamellar spacing of pearlite was 0.125μm when the cooling speed was 4°C/s, the best cooling speed of phase transformation area was during (3-4)°C/s..

Research on Continuous Cooling Transformation Curve of a C-Si-Mn Steel

The CCT curve of a C-Si-Mn steel was investigated. The hot simulation tests at different cooling rates were conducted on Gleeble-1500 simulator and microstructures were observed. Based on transformation temperatures recorded by dilation curves and microstructures, the CCT curve diagram for tested steel was plotted. The effects of cooling rate on microstructure and transformation temperature were studied. The results provide the theoretical basis for determination of hot processing and heat treatment technology of C-Si-Mn steels.

Research on CCT Curve of 12Cr2Mo1R Pressure Vessel Steel

The continuous cooling transformation (CCT) curve of 12Cr2Mo1R pressure vessel steel was measured on Gleeble-1500 hot simulator. The transformation and structures were observed and analyzed. Test results show that with the addition of Cr and Mo, ferrite and perlite transformation temperature increases while bainite transformation temperature decreases, resulting in bainite zone separating from ferrite and pearlite zone. The critical cooling rate for martensite is 30 °C/s.

Continuous Cooling Transformation Behavior of a Ti Addition Steel

The continuous cooling transformation (CCT) behavior of a Ti attached steel was studied through thermal simulation tests, and the influences of different cooling rates on the microstructure and transformation were investigated. The results show that the microstructure changes with the cooling rate, and the CCT curve of studied steel is plotted, which indicates that the solid-state phase transformation mainly consists of four regions. The CCT diagram made it possible to predict the microstructures of studied steel with different cooling rates.

Effect of High Temperature Stays Process on Ultra-Low-Carbon Bainitic Steel without Nb, Ti and other Metal Compounds Forming Elements

The influence of high temperature stays process on the directly cooling experimental ULCB steel had been investigated. We found that the process of high temperature stays had effect on the ULCB steels phase transformation point, and made the CCT curve move to top left. When the cooling rate increased, the formation and growth of granular bainite would be inhibited, but the formation and growth of bunchy bainite would be promoted. And the high temperature stays process had a weaker effect on the specimens structure when specimens were cooled slowly. Key Words: high temperature stays; cooling rate; bunchy bainite; granular bainite

Study on CCT Curve and Microstructure Evolution of a Vanadium-Containing Steel Rebar

The microstructure evolution and hardness change were studied for a vanadium-containing steel rebar at different cooling rates. The experimental results show that bainite and martensite gradual emerged with the increasing cooling rate and resulted in an increasing micro-hardness. Bainite or ferrite and peartite should gradually disappear when the cooling rate increased to a certain value. The cooling rate should be controlled below 10°C/s to ensure good performances. The CCT curve of HRB400E measured with the inflation method and metallographic-Hardness method could provide the theoretical basis for controlled cooling process.

Study on CCT Curve and Microstructure Evolution of HRB500E

The microstructure evolution and hardness change were studied for vanadium containing high strength seismic rebar HRB500E at different cooling rates. The experimental results showed that bainite and martensite gradual emerged with the increasing cooling rate and resulted in an increasing micro-hardness. The cooling rate should be controlled at 0.5°C/s to 7°C/s to ensure good performances of steel rebar. The CCT curve of HRB500E measured with the inflation method and metallographic-Hardness method could provide the theoretical basis for controlled cooling process.

Thermodynamic Calculation and Experimental Study on Complex Phase Steel

Using Thermo-calc software, transformation points as well as bainite starting temperature of the CP steel studied in the present work were calculated. Based on the measured CCT curve, the steels were treated at different conditions using Gleeble-3500 thermal simulation tester. To study the effects of cooling conditions on mechanical properties and microstructure of the steels after austenization, a combination of tensile tests at room temperature, SEM and TEM techniques was applied. Results showed that effective design of chemical composition and heat treatments can be achieved using Thermo-Calc software. The CP steel with carbon equivalent of 0.43% achieved B/M complex microstructure when austenized at 975 °C and followed by isothermal holding at bainitic transformation temperature of 450 °C. The tensile strength is 843.29 MPa and the elongation is 14.28%.